'\" te
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.TH ISSETUGID 2 "April 9, 2016"
.SH NAME
issetugid \- determine if current executable is running setuid or setgid
.SH SYNOPSIS
.LP
.nf
#include <unistd.h>

\fBint\fR \fBissetugid\fR(\fBvoid\fR);
.fi

.SH DESCRIPTION
.LP
The \fBissetugid()\fR function enables library functions (in \fBlibtermlib\fR,
\fBlibc\fR, or other libraries) to guarantee safe behavior when used in
\fBsetuid\fR or \fBsetgid\fR programs or programs that run with more privileges
after a successful \fBexec\fR(2). Some library functions might be passed
insufficient information and not know whether the current program was started
\fBsetuid\fR or \fBsetgid\fR because a higher level calling code might have
made changes to the \fBuid\fR, \fBeuid\fR, \fBgid\fR, or \fBegid\fR. These
low-level library functions are therefore unable to determine if they are being
run with elevated or normal privileges.
.sp
.LP
The \fBissetugid()\fR function should be used to determine if a path name
returned from a \fBgetenv\fR(3C) call can be used safely to open the specified
file. It is often not safe to open such a file because the status of the
effective \fBuid\fR is not known.
.sp
.LP
The result of a call to \fBissetugid()\fR is unaffected by calls to
\fBsetuid()\fR, \fBsetgid()\fR, or other such calls.  In case of a call to
\fBfork\fR(2), the child process inherits the same status.
.sp
.LP
The status of \fBissetugid()\fR is affected only by \fBexecve()\fR (see
\fBexec\fR(2)). If a child process executes a new executable file, a new
\fBissetugid()\fR status will be based on the existing process's \fBuid\fR,
\fBeuid\fR, \fBgid\fR, and \fBegid\fR permissions and on the modes of the
executable file. If the new executable file modes are \fBsetuid\fR or
\fBsetgid\fR, or if the existing process is executing the new image with
\fBuid\fR != \fBeuid\fR or \fBgid\fR != \fBegid\fR, or if the permitted set
before the call to the \fBexec\fR function is not a superset of the inheritable
set at that time, \fBissetugid()\fR returns 1 in the new process.
.SH RETURN VALUES
.LP
The \fBissetugid()\fR function returns 1 if the process was made \fBsetuid\fR
or \fBsetgid\fR as the result of the last or a previous call to \fBexecve()\fR.
Otherwise it returns 0.
.SH ERRORS
.LP
The \fBissetugid()\fR function is always successful. No return value is
reserved to indicate an error.
.SH ATTRIBUTES
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Evolving
_
MT-Level	Async-Signal-Safe
.TE

.SH SEE ALSO
.LP
.BR exec (2),
.BR fork (2),
.BR setuid (2),
.BR getenv (3C),
.BR attributes (7),
.BR privileges (7)
